The invention relates to cathode ray tubes and particularly to cathode ray tubes having a color selection electrode with a plurality of support springs disposed over a plurality of support studs which are affixed to a faceplate panel. At least one of the springs includes an improved securing means for detachably attaching the color selection electrode to the support stud.
In U.S. Pat. No. 3,334,259 issued to T. M. Shrader on Aug. 1, 1967, a shadow mask mounting structure is described. In the preferred embodiment of the Shrader structure, each of the strap-like support springs attached to the shadow mask includes a flat washer having a stud receiving aperture with three projecting fingers which are suitably shaped and inwardly directed to mate with a frustoconical support stud tip. With the mask assembly in position within the faceplate panel and spaced therefrom using a Q-set or panel-to-mask assembly spacer device, the support springs are depressed toward the mask frame and the washers are inserted over the support studs between the straps and the studs, with the stud tips snugly received within the washer apertures. In such an arrangement, the spring action of the support springs urges the washers against the frustoconical tips of the studs to keep the washers in place.
At this point in the fabrication procedure, the washers are still free to move relative to the support springs, and the mask assembly and the Q-set spacer device are still free to be urged together and against the interior surface of the faceplate. Thus, in this condition, a precisely desired Q-spacing between the mask member and the faceplate and a precise alignment of the stud receiving apertures of the washers with the studs can be established.
The washers are then attached to the support springs, such as by temporary tack welding. Then, with the completely assembled mask electrode removed from the panel, a more secure weld using larger equipment is provided. The reason for making the initial tack weld is that the larger welding equipment cannot easily be fitted into the space between the frame and the faceplate panel sidewall when the mask assembly is disposed within the panel.
Experience has shown that since the welding electrodes used to tack weld the washers to the support springs must be relatively thin to fit between the frame and the panel sidewall, the welding electrodes are fragile and require frequent maintenance and replacement. Additionally, the tack welds tend to be relatively weak and often break when the mask assembly is removed from the panel. Thus, a considerable amount of reworking is required at additional cost to attach the washers to the support springs.
It is thus desirable to provide a color selection electrode mounting structure in which a securing washer can be permanently affixed to the support spring while the color selection electrode mounting structure is disposed within the faceplate panel, thereby eliminating the tack welding step of the fabrication procedure.